The molecular organization of the membrane surface of acholeplasma laidlawii will be studied using specific labels for electron microscopy. The effects of the variations in the lipid composition and of lipid phase changes on the distribution of membrane proteins and carbohydrates will be studied. As an additional view of the problem, a cleavable crosslinking regent will be used to study nearest neighbor relations of the membrane proteins. The membrane profile structure will be studied using X-ray and neutron scattering to define the distribution of molecular species across the membrane. Again variations in the state and composition of membrane lipids will be examined. The neutron methods will exploit specific deuteration in different experiments to identify the specific contributions of the various membrane molecular species. These two approaches will provide complementary views of the structure which will combine to give a general view of the molecular organization of the membrane in different states.